Fortunately, WordPress is very easy to update, and there’s really no reason not to be running PHP 7 if this is your main web application. Other applications are more work to upgrade. If you need to upgrade a Zen Cart, for example, please contact me and I’ll help. You can run Zen Cart 1.5.5 under PHP 7.1 with a small number of modifications for most carts.
Open Source but powerful, but with great power comes great responsibility – notably, your responsibility to keep your software updated! If you haven’t upgraded to WordPress 5 yet, this WordPress security announcement should get you into gear. We all knew we’d have to learn Gutenberg some day, it just seems that someday came sooner than we had planned!
I just created a new WordPress plugin called Zen Cart Product Display. Giving it a try right now with OpenCart Discount Chooser: